RT-1183/GRA-114 Transmitter Receiver, Radio Data Link, Sound Ranging. Digitized special purpose communications system capable of transmitting voice when desired and analog representations of signals derived from weapons firings for the purpose of locating these weapons. Uses the +15 Volt tap on a BA-4386 or BA-5598 to power the unit. 133-150 Mhz. Tx Crystal Units The Tx crystal units probably look like small metal box 0.9" x 0.6" x 0.4" high. 2 pins on the bottom about 0.16" apart. These are just overtone crystals. The actual Tx frequency times 2 plus 19.25 MHz is the marked frequency. Rx Crystal Units There are 3 SMB connectors. The input connector takes in the marked frequency and an LO and RF signal are output such that the difference is 18.1 MHz.